This invention relates generally to a device for cooling low humidity air through liquid evaporation, and more particularly to high loft pads for use in such a device and the method of manufacturing such pads.
Application of the principle of humidification or liquid evaporation to accomplish cooling of air has been utilized frequently in the past. Through it, air at uncomfortably high temperatures, usually in excess of 90.degree. F., and with a relatively low relative humidity can be cooled to a comfortable temperature without the need of condenser type air conditioning apparatus with its attendant high energy requirements. Accordingly, this principle has been widely used for air cooling in those arid areas of the world which typically have high temperatures and low humidities.
An evaporative cooling system typically consists of a high volume blower or fan driven by an electric motor, a water distribution system, and cooler pads which are contacted by air and water, the pads providing the surface area whereon the evaporation of the water occurs. In the past these pads have typically utilized aspen wood excelsior as the material for adsorbing and absorbing the water and serving as the media on which evaporation takes place. While this material, at least when new, has proven to be a relatively good material on which to carry out the water evaporation process, it nonetheless has exhibited a number of undesirable characteristics.
Firstly, these wood shavings, by being organic and having a relatively high sugar content, have proven to be effective breeding grounds for various types of bacteria and molds carried by the air. This has resulted in coolers containing such pads soon giving off very objectionable swamp-like odors, and for this reason, coolers employing aspen excelsior have often been called "Swamp coolers." Indeed, as this bacterial action continues on the shavings, the shavings are literally consumed and rendered worthless.
Secondly, as the shavings are continuously contacted by air and water, both containing various chemical and physical contaminants, the light weight shavings soon begin to load up with these contaminants and lose their ability to facilitate water evaporation. This contaminant loading also causes the shavings to sag and shift in their pad frames so as not to be uniformly spaced as desired and so as to destroy their desired air circulation characteristics.
Because of these deleterious effects caused by sustained use, pads containing aspen shavings must be frequently replaced. This is particularly undesirable since such pads are relatively expensive.
To overcome some of these shortcomings, it has been suggested to substitute porous polyurethane material for wood shavings in certain evaporative cooler pads. Such plastic material does eliminate the mold build-up problem to a degree (not being an organic vegetable material like wood), but the plastic still presents problems of its own in operation, in that the moving air does not readily pass through the polyurethane and the water contacting the polyurethane pad is usually not uniformly distributed therein. Also, foam materials of this type have poor resistance to alkalinity and chlorine and fluorine, all of which are particularly present in the waters of the arid areas in which evaporative coolers are most typically used. These deficiencies substantially detract from the operating efficiency and the usefulness of such pads.